There's now a free iPhone app for that, thanks to the U.S. Department of Agriculture.
The application provides a portable reference guide and allows users to learn more about citrus greening, a bacterial disease of citrus that's harmless to humans and animals.
It also allows users to photograph suspicious symptoms on their residential citrus trees, compare the symptoms to images and even send the photos to scientists.
In addition, the app links users to the USDA's Save Our Citrus educational website as well as to a YouTube video about the risks posed by citrus greening.
Citrus greening was first confirmed in the United States in Florida in 2006.
Since then, the disease, also known as huanglongbing or HLB, has cost the state $3.63 billion in lost revenues, according to a University of Florida study.
Recently, a single residential tree was confirmed with the disease in Los Angeles County, Calif.
Citrus greening can reduce citrus fruit production and stunt and even kill citrus trees. It is spread by the Asian citrus psyllid, a small, winged insect.
Download the app for iPhones at the iTunes store.
An app for Android phones is in the works.